In the five years of Project SCAN, we evaluated the development of coronary heart disease (CHD) related lifestyle behaviors including nutritional behaviors, physical activity and fitness, psychosocial factors, and cardiovascular reactivity in a biracial sample of 135 children who vary in their family history (FH) of CHD. A positive FH (FH+) is defined as having one or more biological parents or grandparents with physician verified evidence of myocardial infraction before 55 years of age. A FH- is defined as not having the above history. We propose to follow the children for another four years during which we will focus upon evaluating their cardiac output and total peripheral resistance reactivity to two sets of laboratory stressors which produce predominantly myocardial or vascular responses. There has not been a longitudinal study assessing the relationship between FH, ethnicity, and children's cardiovascular reactivity, especially the hemodynamic regulators of cardiac output and total peripheral resistance, to predominantly myocardial and vascular activated stressors. Nor has any child research assessed the predictive relationships between reactivity and the three markers of CHD risk: blood pressure, left ventricular mass and carotid artery wall elasticity. The proposed research will address these issues and evaluate whether reactivity is a CHD risk factor early in life and, if so, the pathophysiologic mechanisms by which reactivity potentially contributes to CHD will be clarified. The specific aims of the research are to: 1) Examine over four additional years the effects of FH, ethnicity and a select group of moderator variables (i.e., anger/hostility, physical activity, family environment, socioeconomic status) on children's reactivity to two sets of laboratory stressors that produce different hemodynamic patterns of reactivity. Potential moderating influence of exogenous substances and research design factors will be controlled via the study design. 2) Examine the stability over time and across stressors of children's reactivity. 3) Examine whether reactivity during childhood predicts resting blood pressure, left ventricular mass and carotid artery wall elasticity up to seven years later during early adolescence. The general long-term objectives of this project are to understand the early development of children's cardiovascular reactivity within the context of potential moderating variables that may account for or exacerbate FH and/or ethnicity differences in reactivity and to determine the early influence of reactivity upon CHD risk factors prior to overt manifestation of disease. This information may eventually be used to identify children who are at greatest risk for development of CHD and foster the development of family or community-based interventions that may prevent early onset of CHD and improve health.